A guide device for at least one line, such as an electric line of a C-arm, has a rotatable first cylinder with a first cylindrical surface and a static second cylinder, adjoining the first cylinder in the axial direction and having a second cylindrical surface. A first guide element for guiding the line on the first and/or the second cylindrical surface, is disposed coaxially with respect to the first and the second cylinder and it is movable relative to the first and the second cylinder. The line can be wound up on the first and/or the second cylindrical surface or can be unwound therefrom depending on the movement of the first cylinder.